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  3. Black holes. They act like huge drains in the universe. Frightening? Fascinating? Or just fantasy? The very concept of black hol

Black holes. They act like huge drains in the universe. Frightening? Fascinating? Or just fantasy? The very concept of black hol

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问题    Black holes. They act like huge drains in the universe. Frightening? Fascinating? Or just fantasy? The very concept of black holes confuses our common sense notions of matter, time, and space. The theory that black holes can, and probably do, exist in space doesn’ t only concern scientists and astronomers.
   【B1】 For if the theory is valid, we must question all our basic physical laws and, indeed, our "normal" experience of the physical world around us.
   What is a black hole? Well, it’ s difficult to answer this question, since the terms we would normally use to describe a scientific phenomenon are inadequate here. 【B2】 Astronomers and scientists think that a black hole is a region of space (not a thing) into which matter has fallen and from which nothing can escape--not even light. So we can’ t see a black hole. A black hole exerts a strong gravitational pull and yet it has no matter. It is only space--or so we think. How can this happen?
   The theory is that some stars explode when their density increases to a particular point; they "collapse" and sometimes a supernova occurs. The collapse of a star may produce a "White Dwarf" or a "neutron star"--a star whose matter is so dense that it continually shrinks by the force of its own gravity. But if the star is very large (much bigger, than our sun) this process of shrinking may be so intense that a black hole results. 【B3】 Imagine the earth reduced to the size of a marble, but still having the same mass and a stronger gravitational pull, and you have some idea of the force of a black hole. Any matter near the black hole is sucked in. It is impossible to say what happens inside a black hole.
   Our space and time laws don’ t seem to apply to objects in the area of a black hole. Einstein’ s relativity theory is the only one that can explain such phenomena. Einstein claimed that matter and energy are interchangeable, so that there is no "absolute" time and space. There are no constants at all, and measurements of time and space depend on the position of the observer--they are relative. 【B4】 We do not yet fully understand the implications of relativity theory; but it is interesting that Einstein’ s theory provided a basis for their existence. It is only recently that astronomers have begun specific research into black holes.
   The most convincing evidence of black holes comes from research into binary star systems. In some binary systems, astronomers have shown that there is an invisible companion star, a partner to "the one which we can see in the sky. There is one star, called by its catalogue number HDE 226868, which must have a partner. This partner star, it seems, has a mass ten or twenty times greater than the sun--yet we can’ t see it. Matter from HDE 226868 is being dragged towards this companion star. Could this invisible star, which exerts such a great force, be a black hole? Astronomers have evidence of a few other stars too, which might have black holes as companions.
   The story of black holes is just beginning. Speculations about them are endless. There might be a massive black hole at the center of our galaxy swallowing up stars at a very rapid rate. Mankind may one day meet this fate. On the other hand, scientists have suggested that very advanced technology could one day harness the energy of black holes for man’ s use on earth. There are also suggestions that black holes could be used to create bombs in the future, by amplifying radio waves sent up to them. These speculations sound like science fiction. But the theory of black holes in space is accepted by many serious scientists and astronomers. 【B5】 They show us a world that operates in a totally different way from our own and they question our most basic experience of space and time.
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答案我们还不完全理解相对论的含义，但有趣的是，爱因斯坦的理论为黑洞的存在奠定了基础。
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